Study on yaw stability through the response of self-propelled Carangiform fish to impulsive moments

The question of whether fish possess inherent stability remains a subject of ongoing debate. In this study, we assess the yaw stability of a Carangiform fish during free swimming by investigating its dynamic response to impulsive moments. A symmetry airfoil is employed to model the fish body with predefined undulatory deformation. By simulating the motion of a self-propelled fish body under the action of impulsive moments, the dynamic response characteristics of the yaw angle and the fluid moment were analyzed. The results indicate that the self-propelled fish body possesses yaw stability, due to the fluid moment exhibiting both restoring and damping effects. Further research reveals that increasing the amplitude and frequency of the undulation leads to an increase in the restoring and damping moment, thereby enhancing the yaw stability of undulatory propulsion. This implies that the greater the swimming speed, the stronger the yaw stability. Through a comparison of the free and non-free propulsion models, it is shown that the non-free propulsion model has limitations in analyzing yaw stability. This study provides theoretical support for the yaw control of biomimetic underwater vehicles.